(a) Show, giving via suitable diagram, how unpolarized light can be polarised by reflection.
(b) Two polaroids ${\mathit{P}}_1$ and ${\mathit{P}}_2$ are placed with their pass axes perpendicular to each other. Unpolarised light of intensity ${\mathit{I}}_0$ is incident on ${\mathit{P}}_1$. A third polaroid ${\mathit{P}}_3$ is kept in between ${\mathit{P}}_1$ and ${\mathit{P}}_2$ such that its pass axis makes an angle of ${60}^{\circ }$ with that of ${\mathit{P}}_1$. Determine the intensity of light transmitted through ${\mathit{P}}_1,{\mathit{P}}_2$ and ${\mathit{P}}_3$.